Process for the fractionation of petroleum oils



Patented Dec. 7, 1937 a UNITED STATES PATENT OFFICE PRooEss or; THE FRACTIONATION 11 Claims.

This invention relates to the manufacture of lubricating oils from lubricating oil stocks and more particularly to the fractionation of lubrieating oil stocks without application of heat and solely by means of a selective solvent or a solvent'and precipitating agent respectively.

.It is the object of the present invention to provide a process for the cold fractionation of pe- 1 troleur'noils, particularly residuums and distillates thereof, which will effectively separate the residuums or distillates into their various pure fractions and at the same time be much more economical from the commercial standpoint of the products made than any process of fractionation heretofore practiced.

The process according to the present inven-' tion which makes use of secondary alcohols having at least four carbon atoms to the molecule, either alone or in admixture, as selective solvents may-be more easily discussed, and will be more clearly understood by reference to the following specific examples:

Example 1 phuric acid was filtered through fullers earth and was then reduced by distillation with gas to a 29% residuum. This-residuum showed the following properties:

Viscosity s3 210 F. Flash 445 Fire 505 v Pour 5 Carbon residue. 275% Five hundred (500) parts of this residuum were dissolved in 650 parts of a mixture of two parts of secondary amyl alcohol and five parts 40 of secondary butyl alcohol, and to this solution was'added 100 parts of isopropyl alcohol. Instantaneously a substantial part of the dissolved oil was precipitated (precipitate I and solution I).

' Precipitate I (-235 parts) after removal of the alcohol by distillation represented a very light colored oilof viscosity at 210 F. It was dissolved in an equal volume of a mixture of two parts of secondary amyl alcohol and five parts 50 of secondary butyl alcohol and precipitated with fifty parts of isopropyl alcohol (precipitate II and solution II). After the removal of the alcohol from precipitate II by distillation an oil was recovered having a viscosity of 113 at 210 F. and the ol l recoveredrromsoi-utionrm -by Spindle top crude after a treatment with sul- 7 removing the alcohol bydistillation had a vis cosity of 81 at -210 F. 7

Solution I (265 parts), consisting of the unprecipitated oil in amyl alcohol-butyl alcohol mixture solution, was precipitated with parts of isopropyl alcohol (precipitate III and solution III). After the removal of the alcoholfrom precipitate III by distillation, an oil is recovered having a viscosity of 80 at 210 F. and solution III by removal of the alcohol by distillation provides an oil having a viscosity of 72 at 210 F.

We have thus obtained from 500 parts of residuum representing 29% of spindle "to'p crude:

. Per cent Motor oil I, visc. 210 F. 72 --parts=25.0

(Solution III) Motor oilII, visc. 210 80 '140 parts=280 (Precipitate III) 55 0 -Motor oil III,visc. 210 F. 81 parts- 27.0

(Solution II) 1 -Motor oil IV,vise. 21'0F. 113 98-parts=1916 (Precipitate II) Motor oils II and III are of thesame grade and, if desired, they may be combined. Consequently the final products may be as follows:

Light motor 011s, visc. 210'" F. 72 25.0% ofresid.= (Motor oil I) 7.25% sp.(t1p. J v crue. Motor oil, visc. 210 F. 80 55.0% of resid.= (Motor oils II and III) 15.95%"sp. 5p.

. cru e. Aeroplane oil,..visc. 210 F. 113 19.6% of resid.= (Motor oil IV) 5.68% sp. 5p. v(3111 e.

Total motor oils from spindle to'p crudes: 28.88%

Example 2 Fifteen hundred arts of Pennsylvania bright stock having the following characteristics:

Vise/210 F Flash Fire Pour time carbon 152 560 F. 635 F. 16F. 1. 65

The remaining residuum (undissolved stock) was then repeatedly extracted in a similar manner by means of the amyl alcohol-butyl alcohol mixture. The bright stock was finally split up into several fractions with properties as follows:

Titusville bright stock 1500 parts: 100 Extract I visc. 210 F. 152 pour 16 F.

170 parts 11.33% visc.

210 F. 99 pour 14 F.

Since various of these extracts show similar properties it is apparent that, if desirable, certain extracts may be combined without impairing the value of the oil fractions thus obtained.

The following is an example of how the above extracts may be combined so as to form several valuable products.

Extracts I, II and III were combined as also extracts IV, V and VI. Extract VII represents a light cylinder stock and the final residuum a very heavy cylinder stock.

The four products thus obtained from Pennsylvania bright stock together with their properties mixtures of paraffin base crudes secondary amyl alcohol has been found to be the best solvent and in various other cases secondary butyl alcohol is the preferable solvent.

The precipitating agentmay consist of pure isopropyl alcohol but it has been found that a 90% isopropyl alcohol is best suited to the present process. Methyl alcohol or ethyl alcohol may be used in the place of isopropyl alcohol in the fractionation of some oils but it has been found that either methyl or ethyl alcohol is a very powerful precipitating agent and in some cases would give a fractionation that would be too drastic to be of value. The secondary alcohols which constitute the solvent may be pure or may have a water content up to 2% without impairing the necessary reactions of the above described processes.

The alcohols used in the process may be recovered and reused with but a slight loss which should not exceed 1.5% of the quantity originally used.

The finished lubricating oils are absolutely neutral and cannot contain inorganic matter as is often the case in lubricating oils that are purified by acid and caustic soda. Furthermore as a result of the precipitation of the oil fractions by isopropyl alcohol the finished oils are always pure since the impurities mostly organic acids naphthenic acids or compounds of a phenolic nature, are soluble in the alcohols without exception and will therefore always remain in solution. The precipitation may be continued until only the impurities remain insolution, all the oil having and. percentage yields are as follows: been precipitated.

Visc. Visc. Percent Percent Name 130 F. 210 F. F carbon yield Pa. motor Oil I 544 100 520 600 16 1.07 26. 86

A. P. I. grav. 26.2) Extracts I, H, III) Pa motor oilll 650 111 540 615 9 1.26 23.60

(A. P. I. gtav. 26.2) (Extracts IV, V, VI) Pa. L. cy. Oil 840 139 565 635 16 1. 52 9. 67

(A. P. I. gtav. 26.4) (Extract VII) Pa. heavy cy. stk 258 595 650 16 1.88 g 38.67

A. P. I. grew. 25.8) Remaining residuum) It is to be understood that in the foregoing specific examples of the process according to the present invention all viscosity figures are Saybolt values.

The temperature at which the above processes are carried out is not of primary importance. The temperature, however, should be kept constant since a variation of temperature will aifect the quantity of oil being separated in a given fraction, a lower temperature automatically separating out a fraction containing a greater amount of oil.

The proportion of secondary alcohols which constitute the solvent for the oil may vary within a rather wide range, depending upon the type of oil that is to be treated. The mixture referred to in the foregoing specific examples has been found to be the best as a solvent for oil mixtures of a naphthenic nature and is about the same as that produced from cracking still gases in which the gases are acted upon by sulphuric acid. It

'is therefore possible and. very convenient in the present process of fractionation to use the alcohol cut, comprising a mixture of secondary amyl alcohol and secondary butyl alcohol, as produced from the cracking still gases without separating the alcohols fromeach other. In the case of oil.

The lubricating oils produced as in the above two examples are of a particularly high quality. All the oils obtained with the exception of the heavy ends have a rather limited boiling range since it appears that there is no great volatility at 400 F. and there is practically no residue remaining at 600 F. It is apparent therefore that in the actual use of these oils there will be but a slight loss by evaporation and but slight thermal decomposition at higher temperatures. This compares very favorable with many lubricating oils now in use which have a comparatively low initial boiling point and high end point and therefore a comparatively wide boiling range. Oils of this character do not perform well in a motor. Furthermore, the oils produced as in the above two examples have a very low carbon content as compared with many lubricating oils now being manufactured by the application of heat, which fact is of obvious practical advantage in the use of these oils in a motor.

The process according to the present invention is particularly advantageous in the fractionation of lubricating oil stocks in that higher yields of the more viscous oils are obtained by the operation of the present process than by any other method of fractionation now in use.

The petroleum residuums to be fractionated according to the present invention may have been previously dewaxed.

Having described the invention in its preferred form what is claimed as new is:

1. In the production of lubricating oils from petroleum oil residuums, the process which comprises thoroughly mixing the residuum with about an equal volume of a mixture comprising about two parts of a secondary amyl alcohol and about five parts of secondary butyl alcohol, adding to the resulting solution a volume of isopropyl alcohol sufficient to precipitate the desired fraction of oil, mixing this first precipitate formed with about an equal volume of a mixture comprising about two parts of a secondary amyl alcohol and about five parts of secondary butyl alcohol, again precipitating with about half the quantity of isopropyl alcohol previously used, again precipitating the first solution with isopropyl alcohol, and then separating the alcohol from the resulting oil fractions by distillation.

2. In the production of lubricating oils from petroleum oil residuums, the process which comprises mixing the residuum with a solvent comprising a mixture of about two parts of a secondary amyl alcohol and about five parts of secondary butyl alcohol, successively precipitating oil fractions from the solution thus formed by means of isopropyl alcohol, and separating the alcohols from the oil fractions by distillation.

3. In the production of lubricating oils from undiluted petroleum oil residuums, the process which comprises mixing the residuum with a solvent comprising a secondary alcohol having at least four carbon atoms to the molecule to dissolve the said residuum therein and precipitating an oil fraction from the solution thus formed by means of isopropyl alcohol.

4. The process defined in claim 3 in which the solvent comprises secondary butyl alcohol.

5. Theprocess defined in claim 3 in which the solvent comprises a secondary amyl alcohol.

6. In the production of lubricating oils from petroleum oil residuums, the process which comprises'mixing the residuum with a solvent comprising a mixture of secondary alcohols having at least four carbon atoms to the molecule to dissolve the said residuum therein, and precipitating oil fractions from the solution thus formed by means of isopropyl alcohol.

'7. The process defined in claim 6 in which the solvent is composed of a mixture of secondary butyl alcohol and a secondary amyl alcohol.

8. In the production of lubricating oils from petroleum oil residuums, the process which comprises mixing the residuum with a selective solvent comprising a secondary alcohol having at least four carbon atoms to the molecule to dissolve the said residuum therein, and precipitating an oil fraction from the resulting solution thus formed by mixing therewith isopropyl alcohol of approximately 90% concentration.

9. The process of producing a paraffinic lubricating oil fraction from a petroleum lubricating oil stock containing parafiinic constituents and undesired impurities such as organic acids, naphthenic constituents and phenolic compounds, which comprises mixing the oil stock to be treated with a solvent for the stock, mixing isopropyl alcohol with the oil and solvent mixture in suflicient quantity to precipitate out a parafiinic lubricating oil fraction substantially free of said impurities, permitting the said fraction and the dissolved impurities to separate and form a two-layer system and separating the layer comprising the parafiinic oil fraction from the isopropyl alcohol layer containing the dissolved impurities.

10. The process defined by claim 9 in which said solvent is selected from the group of solvents consisting of a secondary alcohol containing at least four carbon atoms and a mixture of such secondary alcohols.

11. The process defined by claim 9 in which said solvent is selected from the group consisting of secondary butyl alcohol,-secondary amyl alcohol and a mixture of secondary butyl alcohol and secondary amyl alcohol.

ERNEST F. EN GELKE. 

